Activation of the inducible cyclooxygenase COX-2 generates significant toxicity in wide range of neurological disease models, in particular cerebral ischemia. However, sustained COX-2 inhibition exerts cardiovascular and cerebrovascular side effects, suggesting that selected downstream prostaglandin receptor signaling pathways may be beneficial. Our previous studies have focused on identifying which prostaglandin receptors mediate COX-2 neurotoxicity and we have determined that although several receptors do promote toxicity, a major finding has been that a larger group of prostaglandin receptors mediates an unexpected and significant protective effect in models of ischemia. Thus, the investigation of prostaglandin receptor pathways downstream of COX-2 has uncovered toxic as well as paradoxically protective signaling pathways, both of which are amenable to therapeutic targeting in models of ischemia. The research objective of this proposal is to expand our investigation of the mechanisms of protection of the PGE2 EP4 receptor, which we have found is significantly cerebroprotective in rodent models of stroke. In this proposal, the cellular substrates and molecular mechanisms that mediate EP4 cerebroprotection with regard to cerebral perfusion and the inflammatory response will be investigated in the murine model of transient focal cerebral ischemia. Genetic strategies using conditional knockout models and pharmacological strategies will be used to identify the cellular substrate(s) mediating protection by this receptor in ischemia and evaluate effects on long term functional outcome measures. Successful completion of these studies will broaden our understanding of endogenous mechanisms of cerebrovascular protection in stroke, and establish the rationale for subsequent investigations in larger animal models of cerebral ischemia to promote accelerated functional recovery, with the long term goal of therapeutic intervention in patients affected by stroke.